Secretary of State Mike Pompeo announced that the United States is withdrawing from the 1992 Open Skies Treaty, saying it is being used to “undermine international peace and security.” The US has been threatening to withdraw for awhile, though Pompeo says the US might consider returning to the Treaty if Russia makes concessions. President Trump went on to say the US might reconsider leaving the treaty entirely at some point.
The treaty is meant to allow the US and Russia, along with other member states, freedom to conduct surveillance overflights of one another. This was intended to be a trust-building concession, allowing each nation the freedom to check and make sure the other isn’t building up a big offensive against them.
In the course of pulling out of the INF Treaty, the Trump Administration has been critical of Open Skies for some time, accusing Russia of not giving them unfettered access to the exclave of Kaliningrad. The Pentagon insisted this meant the treaty no longer benefits the US.
As a practical matter spy satellites probably give the US all the aerial imagery they need, but withdrawing from the treaty is another dangerous escalation of a diplomatic row with Russia. Russian officials maintain they support Open Skies with or without the US.
With the loss of INF, Open Skies, and the imminent expiration of New START, the US and Russia are going to find themselves with few treaties designed to prevent military exchanges, and a lot of new opportunities for arms races. So far there is little sign anyone is going to do anything about it.